Game On
by ThatGoTGirl
Summary: Isabella moves in the Flynn-Fletcher's home while her parents are in vacation. To tease or not to tease? Game on!
1. Chapter 1

**This fic is not related to my previous Phineas and Ferb fanfic, **_**How Ironic!**_

At the height of their 20th Anniversary, Isabella's parents decided that the world is too big to stay in one place. Hence, they packed their bags and left Isabella with the Flynn-Fletcher's. It was the start of their high school year and, while Isabella is glad that her parents are finally off her back, it is a bit weird that she's to spend her whole high school life living with her childhood crush—who she's totally over of. She is definitely _over _Phineas. It didn't take long for her to get settled in. She practically spent her whole childhood on their backyard and Mrs. Flynn-Fletcher would often invite her over for dinner. It only seemed like she was moving into her second home.

Isabella plops herself on her single bed, feeling glad that Candace lent her her room when she went away for college. It has been _three_ _years_ since she's been living in their home and the oldest Flynn is currently studying journalism in the hopes of becoming a gossip writer for one of those famous women's magazine. Isabella might deny this if asked, but she kinda misses the erratic female company.

"Bella, supper's ready."

She lifts her head at the sudden voice from the door, unaware of it even opening. Standing at the doorway is Ferb wearing his sweatpants and nothing to cover his upper body. Despite her awkwardness with Phineas' un-evolving obliviousness with her previous feelings for him, Ferb is the other reason why she still feels a bit uneasy after all these years with her living with them.

It all started freshman year. Ferb, the boy who would always _always _be by Phineas' side and nowhere else, came home late. Mr. And Mrs. Flynn-Fletcher, not used to him arriving later than Phineas, started panicking. As usual, Isabella's fireside instincts kicked in and she managed to calm them both with a cup of tea. A few hours later, Ferb came in wearing a hoodie—_a goddamn hoodie_—and sweatpants with a towel around his neck. Candace almost tackled him with need for answers and he merely shrugged and answered in that cute British accent of his that he's been to the gym. It took some getting used to but it eventually became a routine. They would all wait for Ferb to come home from the gym and eat dinner together—of course, after he showers. But what troubled Isabella the most is that he seemed to appoint himself to be the one who always calls for her whenever dinner was ready. Not that she's complaining about his chivalry but, quickly after he's been exercising at the gym regularly, he developed these abdominal muscles that definitely spend too much time on her imagination. Even the girls at school began to notice the physical change in Ferb. They all called her lucky that she lived with the British stud and his charming brother. _Pssh_. Agonizing is the word that she would use living with them.

"_Bella?_"

She realizes that she's been ogling his bare, sculpted chest for quite some time. "You know you could just use the nickname that everyone uses for me: _Izzy_,"

The smirk on his face is enough to send butterflies swarming her stomach. "Then I wouldn't be special."

She stands up from her bed and sashays towards him. "Who says you're special?" With a quick kiss on his cheek, she leaves him grinning to himself.

It's not just hard for Isabella. It's also hard for the brothers too. Adorable or not, Phineas and Ferb are hormonally-infested teenagers.

For Phineas, it's like suddenly realizing how attractive his best friend is. When he was eight years old, he's always found her helpful. The way she's always there to help has always cheered him up. When middle school came, he had to endure comments from his guy friends on how cute Isabella is. It continued till high school where comments turned from 'cute' to '_Isabella is goddamn hot! Hey, let's make a bet on who gets to make out with her first_' or '_Damn Flynn, you're so lucky to be living with a hot ass like that_'. Of course, his guy friends spent most of their free time in the Flynn-Fletcher home in the hopes of landing a date with the sweetheart.

It's not like he _likes _her. He's just _mildly attracted_. Isabella has always been cute but watching her turn into a bombshell at every party they attend is hard for a teenager like him. He's never really dated much and only spent four months at the most with a girl before he becomes bored because..._well_, teenage girls only like to talk about themselves and their social status. Teenage girls that do not include Isabella. It seems like his childhood friend has not only grown beautiful but also intellectual. He found himself always in a verbal battle with her during dinner while his parents and Ferb watched amusedly.

"She liked you when we were kids, you know?" Ferb told him this one night at their usual midnight musings. Even if they're in high school, they do not attempt to change rooms since they've been always comfortable with each other's presence.

This startled him awake because this is new information.

Ferb snorted in the bed beside his, also sitting up. "Tell me you haven't been _that_ oblivious, brother." Ever since his stepbrother started going to the gym, Phineas has always been conscious of how his brother is snagging all the attention with no trouble at all.

"I had no idea!" Oh how things could have changed if he knew.

"It doesn't matter now. She's over it." And that's when he knew how late he really is. The sharp edge in Ferb's voice only proved that his brother has some feelings for their current housemate.

The next couple of days, Phineas noticed how the two of them would keep sending each other subtle glances. Before, this was only a shrugging moment for him that Ferb and Isabella are only curious about each other. Now, he couldn't help but also notice the way the two of them would gravitate towards each other during breakfast...the way his brother would escort Isabella towards her locker everyday at school and the latter smiling like Ferb just saved the day whenever he offers to carry her books for her...how both of them would be smiling so wide everytime both of them comes down for dinner...how Isabella sends a wink towards Ferb every night when she says good night to them wearing those short nighties. Yes, he's too late. Definitely too late.

Unlike his American brother, Ferb has always known about Isabella's beauty. He knew ever since he first met her when she and her mom welcomed them in the neighbourhood. She was wearing a puffy pink dress, hiding behind her mama's skirt. Ferb, more talkative then than he is now, smiled widely at her and asked her if she wanted to play. Of course, their friendship was put aside once the young Isabella set sights on the more cheerful and friendly Phineas. Ever since they were kids, Phineas always gets more friends. It seemed like the cute British boy is bound to be the cute loner.

He had to endure her fawning over his stepbrother their whole childhood. He could not help but think of how unfair everything seemed. It was not fair how Phineas got the friends _and_ the girl. Still, he could not let the envy invade him and he settled in comfortably as Phineas' assistant. He even managed to let go of his little crush with Isabella and exchanged her with the darker and _older_ Vanessa Doofenshmirtz.

This all changed in middle school after their small, yet highly functional, family returned from their vacation at the Caribbean islands. Puberty kicked in for the stepbrothers yet it seemed that it beat the hell out of Ferb. He didn't bother cutting his spiky hair during his short bohemian phase during their vacation. Lawrence Fletcher told his son that his developing green curls were inherited from his birthmother. When they returned to Danville, his friends were all surprised that his spiky hair was gone and was replaced by soft, luscious curls just resting two inches above his neck. Not only that but his voice developed into a husky British accent that won over every girl as soon as the first word from his mouth comes out. Suddenly, he started getting all the girls' attention. His athletic abilities also stood out and every guy wanted to be his best friend. His attitude didn't change though. He's always been comfortable behind Phineas' shadow.

It took him by surprise when his parents announced that Isabella would be living with them temporarily for the start of their secondary education. Their friendship endured the confusing minds of tweens so it would not be awkward for him to be seeing so much of her. After all, she—besides Phineas—is the only other person in their school that he's comfortable talking with.

Comfortable is definitely _not_ the word. Isabella is a nightmare to be living with. He discovered this a few months after she settled in. She has made it her mission to make him more talkative by constantly teasing him. There is one time that they swore _never_ to talk about again. Ferb acted on his hormonal teenage male instincts and took a willing cheerleader home while his parents spent another night in an antique convention. Isabella's daily student council meetings ended too early and she caught him in a very compromising position. They both blushed furiously and, for weeks, ignored each other as best as they could.

"Hey, can we forget all about what happe—oh my God!" Isabella burst inside his room one day, finally fed up with their silent friendship. Her hands covered her eyes as soon as she discovered him doing push ups wearing just his sweats.

His next action changed the course of their friendship. Feeling a bit mischievous, Ferb stalked towards her like a prey and wrapped his muscular arms around her lean waist, pulling her inside his room. His other arm closed the door behind her and he found himself caging her small body using his muscular one. He blames it on her tank top and boy shorts.

"It's okay to look, love. I'm not in the nude." He pried her hand away from her face.

Her sharp intake of breath pleased him. "What are you doing, Ferb?"

He merely shrugged, bending over to tease her a little bit. When she closed her eyes in anticipation, he stopped leaning in. "You were telling me something?" He whispered once his lips are close enough to brush against hers.

This embarrasses her as her eyes fly open and her fingers stopped clutching his soft green curls. "I—I was j—just..._fuck_...are we okay? I mean, c—can we just forget what happened a week ago?"

He decided that he liked it when she rambled so he teased her a little bit more. "Oh, you mean your ogling at my chest?"

A snort escaped her lips. Her fire is back. "_I did not ogle at your chest_! I was referring to me witnessing your hormonally infested activities with cheerleader Mindy!"

"Oh..._that_."

"Yes, that!" She pushed him away with her tiny hands. "So are we good?"

He shrugged, basking in the glory of witnessing the darkened blue of her eyes. "Yes, we're fine."

"Good," She says with finality before throwing his door open and rushing out.

"You look divine when you're angry!" He shouts after her, laughing loudly when he hears her cry of frustration.

He definitely likes frustrated Isabella.

Ferb regrets his actions. Their short teasing episode only resulted in turning the game on for Isabella. First, it was just intriguing slow licks at her spoon during breakfast while she stared at him tauntingly. He couldn't count the amount of he had the urge to take a cold shower in the morning because of that. Then, it turned to her wearing scraps of cloth that she waved off as her night clothes because of the heat of the impending summer. Her 'clothes' showed too much skin that even sweet, oblivious Phineas has drool running down his mouth every time she bids them good night.

What broke his crumbling control is coming home one night when he thought that he had the house to himself for the first time since Isabella moved in. Mum and Dad joined a couples camping trip with Baljeet's parents. Phineas was spending the night with his science club friends after going on a date with Ginger. Isabella announced this morning that she will catch up all night with her previous Fireside girlfriends—no doubt only agreeing to stay over because she wants to grill Ginger about her date with Phineas. It pissed him off, to be honest, that she might still harbour some sort of crush for his stepbrother.

He took a refreshing shower, washing away all the sweat from the gym. He didn't bother taking any clothes with him since he's alone. Hence, that is how Isabella found him. As soon as he saw her inside his and Phineas' room he realized that he has nothing but a towel wrapped around his waist just below his v-lines.

"I thought you were sleeping over with the Fireside girls?" He inquired, raising his dark eyebrows at her sitting form.

She nodded, a small sly look on her face. "I _was_ but then I decided that there is no place like home."

"Okay?" He ran his hand through his wet locks, taking large strides to his underwear cabinet.

"Ferb?"

"Yes?" _Where are my lucky green boxers?_

"It's laundry day yesterday and I hope you don't mind..." Isabella trails off.

He turned around and the liquid on his throat dries up instantly. _Holy fuck_. She was standing in front of him, wearing his green boxers and loose fitting white shirt. It looked like she's wearing nothing else but the shirt because of its length. The green just resting above her thighs proved otherwise. Her dark hair was tousled like she messed it up while he was looking for his boxers. She was not wearing any makeup but the obvious smudge under her eyes suggested that she previously washed it off.

"_Holy cow_," She looked like she just spent the whole night making love.

Her hips swayed agonizingly as she walked towards him. "Is this alright, Ferb?"

"Fuck it." He all but pushed her on the nearest bed, taking her mouth in his. She tasted of sweet strawberries and mint and he couldn't get enough of her. His hands found themselves under the confines of her—_his—_shirt. _Holy smokes, she's not wearing a bra_. She moaned as he trailed his fingers down the edges of her stomach, wrapping her long legs on his waist. The skin to skin contact is enough for him to groan in anticipation. Is she really doing this with him?

Her hands were everywhere, either gripping his wet hair or trailing her nails at his bare back. Then at his chest...pushing him flat on his back with her straddling him. His tongue traces her bottom lip, a groan escaping him when she allowed him access. He has absolutely no self-control in the moment.

Then she's gone.

"Good night, Ferb."

_Phineas is going to murder him for what they did to his bed_. "Bloody. Fuck. Me."

**Aha! Another idea that I simply cannot get out of my mind. Hope you like it **** It's a bit AU since i didn't have Phineas and Ferb build any contraptions.**


	2. Chapter 2

**Game On**

**Chapter 2**

Oh it is definitely game on! Isabella hid her smirk behind her coffee cup the morning Ferb comes down for breakfast. He didn't sleep well judging from the tired look he's sporting. His long hair is messy, giving the impression that he spent his morning running the fingers through it a couple of times before deciding to do down and get breakfast. Phineas would probably be home late at night and Mr and Mrs Flynn-Fletcher said that they would be arriving at three o'clock.

"Good morning Ferb," She greeted him good morning and checked to see if the breakfast that she made for him still looked nicely.

The look that he gave her resulted in butterflies in her stomach. Too bad she already changed out of his clothes.

"Lovely morning, isn't it Bella?" His husky British voice would become the death of her someday.

They spent a quiet breakfast together, each not knowing just what to say to the other. Ferb bailed on his t-shirt since the hot weather of June is fast approaching, which leaves his sculpted chest bare for her to gaze at. Hmm...she remembered how his pale skin felt against her palms. So smooth and so hard...

"See something you like?" His voice snapped her back to reality.

The smirk that he's currently sporting would make the teenage girls of Danville High cry out for him to date them. He's a stud and he doesn't know it. "_Mayyyybe_," She decided to tease him.

It was definitely the wrong time for him to sip his coffee since he became a spluttering mess as soon as he heard the suggestion in her tone. "Don't insinuate something that you can't finish, Bella."

Isabella rinsed off the remaining crumbs off her plate before setting it on the counter. She walked slowly towards Ferb and planted one on his mouth. It is a fact that she just recently discovered last night. She likes kissing him. "Who says I can't finish this?"

"_Bella!_" She finds his growling veeery attractive.

"Game on, Brit!"

"Whooooo is it hot in here or is it just me?" A couple of girls sighed at the sight of a shirtless Ferb. Today is Danville High's fund-raising and Ferb and his football teammates are currently contributing for the construction of the new school auditorium in the means of a Car Wash. Supposed to be, it would only be the cheerleaders and the jocks but somehow it turned into a school thing.

Their game officially started last week and Ferb decided to leave a huge bomb on their battlefield by letting everyone know that he's been working out. Isabella watched from behind a dirty road truck the way the cheerleaders would faun over his biceps and use towels to wipe the sweat off his forehead and neck. _What a bunch of needy teenagers_.

"Whoa, Izzy. What did that road truck do to you?"

Startled, Isabella started firing the hose on the person behind her.

"Whoa no stop I come in peace!" The younger Flynn-Fletcher raised both his hands in surrender as he discarded himself of his wet shirt.

"Oh Phineas! I didn't see you there. Sorry!" She meekly grinned as an apology.

"It's fine Izzy." Then he turned around for the people watching. "I'm fine people!" They laughed at him in response. The girls might be Ferb's but their friendship would always belong to Phineas. He will always be the sweet, talkative one. It must be why Isabella wanted to marry him when they were younger. She wanted to be friends with everyone and Phineas is _definitely_ friends with everyone.

Noticing that his stepbrother is currently watching, Isabella slyly faced the redhead. "_Wow Phineas_...you've been working out, haven't you?"

He turned as red as his hair because of her suggestive tone. Oh she feels like a total slut flirting with him like this when all she really wants is to take his handsome and dashing British brother home and have her way with him. The world has definitely turned and she wants the attention of the brooding mysterious older Flynn-Fletcher instead of the oblivious, kind, friendly Phineas.

"Uuuh yeah, I've been joining Ferb at the gym recently. I'm glad you noticed." He ran his hands on his hair before joining her to clean off the dirty truck. While not as muscular as his older stepbrother, Phineas is certainly coming along. Granted he will never be as handsome as Ferb, he comes at a close second. Besides, his extrovert personality wins him more than the older boy.

"I've definitely noticed."

Alarms blared off as a car was hit too hard. This stopped her from continuing her flirtation with the younger Flynn. The students were desperately looking for the owner of the car to stop its noise. Isabella looked around and saw a green-haired boy furiously shaking his hair as he walked out of Danville High's parking lot.

"Uhm...Isabella?"

"_What?_"

"Why are you stabbing your ice cream manically?"

_Funny question, Gretchen. It seems as if Ferb has made it his mission to ignore me these past few days and finally made it an effort to use his British charms of high school girls and parading himself with a different girl in his arm everyday at school—while still pretending that I'm invisible, of course. Now, he's laughing and chatting with the gorgeous college girl, Vanessa, whom he's had a crush on since forever and all I want to do it stab her with my plastic spoon and rub the sticky ice cream all over her perfect face. _"I'm just not in the mood to eat ice cream, Gretch."

"Wait...you're the one who invited me for ice cream!"

Isabella waved her off and took out her phone to text him.

**From: Isabella**

**To: Ferb**

_**So I guess she's back huh?**_

She gets a reply a few seconds later.

**From: Ferb**

**To: Isabella**

_**Jealous?**_

The nerve!

**From: Isabella**

**To: Ferb**

_**You wish, darling.**_

"Izzy, who are you texting?" Gretchen peeped on her phone and gasped loudly once she sees the previous messages. The ex Jr. Captain of the Fireside girls scanned the ice cream shop before averting her eyes from the intrigued Ferb. "Oh my Gosh! Are we spying on Ferb?"

"Shhh!" She places her index finger on her lips, aware that the boy they're talking about is currently on a date with some other girl a few feet away from them. "Be quiet or he'll hear you!"

"Isabella, what is happening?"

And this is how she found herself a couple of hours later: with tear-stained face and lips almost blue from all the cold yummy goodness. She managed to tell Gretchen everything. From the moment she moved in to the present when she managed to convince her friend to eat ice cream with her while she spies on her frien—no, boyfriend? No...lover? Ugh. Looks like she needed the ice cream after all.


	3. Chapter 3

**Final chapter! Whoo hoo! Okay so I didn't really plan for this to have three chapters. It's supposed to be a one-shot. Hope you guys enjoy!**

**Final Chapter**

_**And this is the end of our beginning**_

An arm catches her off guard as she manoeuvred her way towards the Flynn-Fletcher's dining room. Ferb did not call for her just like he did the past couple of days. It not only confused her but the rest of the household too. They all knew that she and Ferb were the closest out of all of them.

"You've been crying," It is a statement, not a fact, as the older Flynn-Fletcher dragged her back inside her room. In moments, he had her pinned against her wall while she looked anywhere besides his eyes.

His hold was not as caging as it was meant to be since her weak push managed to make him back up a couple of steps. "Dinner's waiting, Ferb."

He pulls her back once again when she tried to walk out on him. "I don't care about supper. I care about what's making you cry!"

Suddenly, she's not sad anymore. She's mad as hell. "Do want to know what—who—made me cry?—" She did not give him time to reply since she's banging on his chest like a small child. "—_You!_ You made me cry, you stupid, hot, gorgeous, confusing Brit!"

"_Me?_" He was pointing to himself, surprised by sudden escalation of their conversation. "How in the world did I make you cry?"

She slaps him chest rythmically. "When you went on an ice cream date with Vanessa Doofenshmirtz and acted like a couple with her!"

His sudden laugh surprises her. "We were—what you Americans affectionately call—_catching up_!"

_Does he think she believes that bullshit? _"Believe me, there was nothing to catch up on once she started with her lingering touches—no, not just lingering, her hand stayed long enough in your biceps enough to call it caressing in a public area!"

"Like you haven't been fraternizing with my brother during the car wash!"

The anger in his voice started her. Never before has Ferb raised his voice. Seeing him almost explode surprised her and she doesn't know whether to be proud or annoyed at herself for bringing this side of his. "_What?_ I wasn't flirting with Phineas!"

"'_Oh Phineas, you've been working out'_" He tried to mimic her meaningless flirting. "Could you be any more obvious that you're still in love with him?"

"_We're playing a game_!"

"That bloody game! You know what I think, Bella? You're bored. You are so bored that, just because Phineas doesn't pay any attention to you, you turn your sights to the other Flynn-Fletcher boy who was only too willing to play with you this vile, manipulative game!" Somehow, their chests ended up being pushed too close together and their breaths mixed in the heated discussion.

"I am _not_ in love with Phineas!"

He scoffed.

"...because I'm in love with you." There. She said it. No more going back now.

"_What?_"

"You talk too much, Brit." Then she closed the space between. Their lips melted passionately, each making up for the lost time and the one spent teasing each other. Oh why did she ever decide to start that stupid game? She's glad that she decided to wear a dress today because of the hot winds so it became easier for her to jump in his arms and wrap her bare legs on his waist. The back of his legs hit her bed and she squeaked in surprise when they fall on the bed. She straddled him while he quickly sat up and removed his shirt. Yes. It is a fact that Isabella will never get tired of seeing Ferb shirtless. His tongue traced her bottom lip and she eagerly accepted his taste on her mouth. How is it that he managed to taste like dark chocolate all the time?

She ran her fingers through his already messy tresses, untying his man bun. Some people might call guys with long hair weird, but Ferb's hair has always turned her on. Oh he has great hair. A loud moan escaped from her lips once he devoured her neck. Her eyelids fluttered when she felt him sucking on one particular soft spot.

"Oooh yeah, right there." She bites on his shoulder once he fulfils her wishes.

He groaned when he fumbled for the straps of her dress. "Why didn't you just wear the ones with zipper?"

"Because those are not as alluring as this one." She giggles when he bites the straps off her shoulders in frustration.

"You got that right." She gripped his hair when she felt his lips on her collar bone and getting lower...and lower...

"_Boy this is not what I expected when I come home!_" A feminine voice sprang them apart. Isabella fell off the bed and into Candace' furry carpet. The owner was standing on the door; arms crossed her chest with a face looking smug.

"Welcome home sis," Ferb mumbled, grabbing a pillow in an attempt to hide his straining trousers.

"Well I'm glad that you two finally acted on the sexual tension. Dinner's ready, by the way," Before she walked away, she looked directly at Isabella. "You better find good makeup to hide that forming hickey on your neck."

Isabella's hand flies on her neck, feeling the tender spot in embarrassment. Well, Candace _did _say that she's glad for them, right?

She feels a hand gently helping her up from the ground. "You all right, love?"

"Yes, I'm fine." She lifts the straps back up her shoulders and fumbles for concealer on her dresser. "We have to make it fast, dinner's ready. I need to cover your way of marking your territory and you have a tent in your pants that needs to be put down."

He chuckled, appearing behind her in the mirror. They've never really taken a picture together as teenagers. Yes, they're definitely good together. He kissed her shoulder one more time. "By the way, I love you too."

Holy shit. Total relationship goals moment. A wide smile takes over Isabella's flushed face. Finally they're on the same page. They're a perfect match, from looks to I.Q. It only took a couple of months of teasing for them to realize their true feelings.

"Hey Ferb?"

"Yes?" He swings around from the doorway.

"Game's over."

**And that is the END! Tadaaaaaaaaaaaaaa It isn't very long and, honestly, I'm not very proud of it. I'm a very big fan of Ferbella and we need MORE FANFICS about them.**

**Please review hehe i love reviews!**

**Check out my other Ferbella fic. It's titled How Ironic.**

**Lots of love! **


End file.
